1. Field of the Invention
The present invention relates to a configuration and a control of an Auto Document Feeder (ADF).
2. Description of the Related Art
In a field of an image reading device such as a copy machine, a facsimile, and the like, there is known an Auto Document Feeder (ADF) configured to automatically feed a document.
In a case where a document feeder is provided with only one reading device, a document needs to be turned over such that both sides thereof are read. An ADF thus may be configured to be capable of turning over the document in some cases.
As a method for turning over the document by the ADF, a method for turning over the document by feeding the document in a switchback manner (a switchback method) is commonly employed.
Furthermore, as a method for turning over the document, there is also known a configuration in which the document is fed in a U-turn manner (a U-turn method).
In a case of employing the U-turn method, there is a problem in which since the number of rollers to feed the document in the U-turn manner is increased and thereby the number of components is increased to handle a document having a long length in a feed direction, the ADF increases in size, which leads to increases in cost.
In this respect, since there is not a problem as described above in a case of the switchback method, there is an advantage in which the ADF can be reduced in size. In the switchback method, however, since the feed direction of the document is reversed, feeding the document takes time. Thus, in the case of employing the switchback method, reading the document at a high speed is difficult.
There is publicly known a reading device configured to switch paths for a U-turn according to a length of the document. Since the reading device feeds a short document in a U-turn path for a short document and feeds a long document in a U-turn path for a long document, both the short document and the long document can be handled. However, the reading device still forms a path for the long document to perform a U-turn within a device of the ADF. The reading device thus cannot resolve the problem in which the device increases in size to be capable of reading both sides of the long document.
As an art not related to the reading device, there is publicly known a recording device configured to switch a U-turn feeding and a switchback feeding according to a type or a size of a paper. However, an object of the above-described recording device is not to damage a coating surface of a special recording paper, and thus the recording device is regarded as an art not related to the ADF that feeds a document.
In the above-described recording device, the switching between the U-turn feeding and the switchback feeding is performed when feeding a recording medium to record on a first side thereof. When turning over the recording medium to record on a second side thereof after recording on the first side, the recording device performs the U-turn feeding irrespective of the type or the size of the paper. Therefore, even if applying a configuration of the above-described recording device to the ADF, similarly to the above-described reading device, the recording device cannot resolve the problem in which the device increases in size to be capable of reading both sides of the long document.